1. Field of the Invention
The present invention is directed to an outboard motor for a watercraft, and more particularly to an arrangement of engine components of a marine outboard motor.
2. Description of the Related Art
There exists in all fields of engine design an increasing emphasis on obtaining more efficient emission control, better fuel economy and, at the same time, continued high or higher power output. Accordingly, two-stroke type internal combustion engines have recently become more popular for use in watercraft due to their relatively high specific output ratios (e.g., horsepower per cubic centimeter). However, there are certain objections to the use of two-stroke powered watercraft on some bodies of water. For example, environmental issues arise when two-stroke internal combustion engines are used on small bodies of water, due to the lubricants, unburnt fuel, and other byproducts that are often contained in two-cycle engine exhaust. These environmental concerns have raised a desire to minimize exhaustion of hydrocarbons and other exhaust byproducts (e.g., carbon monoxide and oxides of nitrogen), and thus reduce pollution of the atmosphere and the body of water in which the watercraft is operated.
These trends have resulted in the substitution of fuel injection systems for carburetors, as the chargeformer of two-stroke engines. In the commonly used systems, fuel is injected into an intake air manifold. In order to obtain still further improvement, direct injection systems are being considered. These systems inject fuel directly into the combustion chamber and may be accompanied by stratification or lean burning operation to further fuel economy and emission control.
Direct injection, however, requires that the pressure at which fuel is injected into the engine is higher than the pressure required for manifold injection systems. Fuel systems for direct injection thus must supply fuel to the fuel injectors at extremely high pressure in order to inject fuel into the corresponding combustion chambers as the combustion chambers reach their minimum volume (i.e., where the piston nears top dead center).
High pressure fuel pumps are typically employed for producing highly pressurized fuel for direct injection purposes. Conventionally, in V-type engines employed in outboard motors, a high pressure fuel pump used for direct injection purposes is directly driven by the crankshaft of the engine via a drive belt. However, high pressure fuel pumps and their drive units are large and are therefore typically mounted in the valley created between the cylinder banks which form the V-type engine.
In order to protect the internal combustion engine and to smooth the air flow over the engine, an upper cowling is typically mounted over the internal combustion engine of an outboard motor. Because outboard motors are often used at high speed, and since the upper portion of an outboard motor which contains the internal combustion engine oftentimes extends above the transom of the watercraft to which it is attached during operation, the shape of the upper cowling has a significant impact on the aerodynamics of the watercraft. Therefore, the upper cowling desirably is sized and shaped to fit tightly around the outer contours of the internal combustion engine and create a symmetric flow of air around the engine.
A need therefore exists for an outboard motor that includes a direct injection in-line engine that has a compact arrangement. It is desirable that the components of the engine are arranged so as to minimize the entanglement of the electrical conduits and fuel lines which connect the various components of the engine. Additionally, it is desirable that the engine of the outboard motor have a shape such that its frontal area is generally symmetric, so that an upper cowling can be made as small as possible.
According to one aspect of the invention, an outboard motor includes an in-line type, direct injected, two-stroke internal combustion engine having at least one cylinder, extending about a longitudinal axis, an electrical system arranged substantially on one side the longitudinal axis, and a fuel delivery system arranged substantially on a second side of the longitudinal axis, opposite the first side. By providing the fuel and electrical systems on opposite sides of the longitudinal axis of the cylinders, the present invention provides a simplified layout for an internal combustion engine of an outboard motor.
For example, the fuel system of an internal combustion engine includes several components connected by fuel lines. Similarly, the electrical system of an internal combustion engine has a number of components connected by electrical conduits. Conventionally, when such components have been installed on an engine, the fuel lines and electrical lines may be overlapped and intertwined with each other, thereby forming a complex component layout that is difficult to service. Additionally, because the internal combustion engines of outboard motors are covered by a removable cowling, essentially every component of the internal combustion engine is mounted directly or indirectly to the engine body. Mounted as such, the various components of the internal combustion engine and the engine body form a compact unit. However, by mounting the various components in such a manner, servicing of the engine becomes more complicated due to the tight spacing and intermingling of the fuel and electrical lines.
By arranging the fuel system and the electrical system on opposite sides of an internal combustion engine, the present component layout provides a compact power head and simplifies the arrangement of these engine components. For example, with the fuel and electrical systems arranged as such, the electrical conduits connecting the various components of the electrical system remain separated from the fuel lines which connect the various components of the fuel system. Therefore, servicing the electrical and fuel systems is simplified.
For example, when servicing a fuel or electrical system, it is necessary, when performing certain repairs, to trace the path of an electrical conduit or fuel line. If the electrical conduits and fuel lines are intertwined, it may be difficult to determine where the fuel lines or electrical lines lead. However, with the fuel and electrical systems arranged in accordance with the present invention, the pathways of the fuel lines and electrical conduits are more easily viewed when servicing the engine. Additionally, with the fuel delivery and electrical systems arranged on opposite sides of the engine, the components of each system can be closely spaced to each other, thus further compacting the engine""s size. Additionally, the length of the electrical conduits and fuel lines are minimized, thereby reducing the cost of component materials.
Another advantage stemming from the separation of the fuel and electrical system is that the overall size of the engine is compact, thus allowing a tight-fitting cowling to be fit over the engine with little wasted space. As discussed above, since the upper portion or the powerhead of an outboard motor is subjected to significant airflow during operation, it is desirable to shape the upper cowling so as to minimize aerodynamic drag. Thus, it is desirable to minimize the frontal area of the cowling.
In order to provide optimal airflow around the upper cowling, the cowling also is desireably symmetric. If an engine component extends laterally outwardly from one side of the engine, requiring a projection to be formed on the cowling to extend around the projecting component, an identical projection would be formed on the opposite side of the cowling so that the airflow around the cowling is symmetric. It thus is important to arrange the components of the internal combustion engine symmetrically around the engine body. By providing the fuel system on one side of the engine body and the electrical system on the opposite side, the resulting engine layout can be made generally symmetric with respect to the longitudinal axes of the cylinders. A tight fitting cowling thus can be fit over the engine with little space wasted.
Further aspects, features, and advantages of the present invention will become apparent from the detailed description of the preferred embodiments which follow.